Flip-chip packaging relies on solder to connect the IC to the package. These solder interconnects are called bumps. The bumps have traditionally been made of Pb/Sn alloys. However, with the advent of legislation restricting the use of lead, the electronics industry is being pushed to Pb-free alloys. For example, the Restriction of Hazardous Substances (RoHS) directive, adopted by the European Union in 2003, restricts the concentration of lead in any homogeneous component to 0.1% (1000 ppm) or less. The most prevalent Pb-free bump alloys are ternary Sn/Ag/Cu and binary Sn/Ag. The Sn/Ag alloys are typically plated, while the Sn/Ag/Cu alloys are typically paste printed. In the case of plated Sn/Ag, the under-bump metallization (UBM) is typically a tri-layer of Ti/Cu/Ni; for the Sn/Ag/Cu alloy, the UBM is typically Al/Ni/Cu.